This invention relates to a latch needle having a head (hook) cooperating with a pivotally supported latch. The latch needle further has a needle cheek which is provided with a sawslot defined between two side walls of the needle cheek. The latch has a latch shank accommodated in the sawslot and provided with a latch hole. The latch needle further has at least one latch bearing which is formed by at least one projection constituted by a plastic deformation of at least one of the cheek side walls. The material from which the projection is formed leaves a depression in the respective side wall. The projection extends into the hole of the needle latch. Latch needles of this type are used, for example, in knitting machines.
The latch may be pivoted into a first position in which the latch lies on the free end of the needle head and a second position in which the latch is swung away from the head and thus opens the same. In this arrangement an accurate support of the latch is very important. The latch has to move freely to ensure that it may be pivoted back and forth by small operating forces. On the other hand, the latch has to be guided with such an accuracy that, in the course of the closing motion, the latch spoon arrives into a precise engagement with the hook. Such a result has to be ensured for the entire service life of the latch needle.
As noted earlier, the latch is usually supported on the latch needle by a pin extending through a latch hole which is provided in the needle latch for this purpose. In the vicinity of the needle head a cheek region is formed which has a sawslot. On both sides of the sawslot side walls are arranged from which a pin is formed or between which a separate pivot pin is held. The latch shank extends between the side walls into the sawslot and journals on the pin.
Various embodiments have become known for forming a pin to support the latch or for inserting a pin into holes provided in the side walls of the needle cheek. Thus, U.S. Pat. No. 3,526,104, to which corresponds German Offenlegungsschrift (application published without examination) 15 85 091 discloses a latch needle having an inserted pivot pin. The holes which are provided for receiving the pivot pin in the side walls of the needle cheek are in alignment with one another and conically flare towards the outer side faces of the needle. The pivot pin is a separately made wire component which is inserted into the aligned holes and is riveted at both ends whereby convex rivet heads are formed.
U.S. Pat. No. 5,509,280 discloses a latch needle in which, for supporting the latch, two obliquely adjoining half pins are provided which are pressed out from the side walls defining the sawslot. The half pins are of asymmetrical configuration related to the pivot axis of the latch. The half pins are formed by plastically deforming the side walls with a suitable puncturing tool. The penetration depth of the tool is not constant along the circumference of each pin, whereby the flow conditions of the material are not uniform along the circumference.
Further, for supporting a latch on a latch needle, it is known from German Patent No. 608,619 to make half pins by plastic deformation of the side walls on both sides of the sawslot. For this purpose, puncturing tools with planar end faces are used. The puncturing tools have at their frontal end a cylindrical bit with a planar end face whose diameter is smaller than the diameter of the half pin to be made.
The half pins form projections which extend into the sawslot and penetrate into the latch hole. The purpose of this arrangement is to ensure a lasting, accurate positioning of the latch.